1,1-Dichloro-1-fluoroethane (hereinafter referred to by its American Society of Refrigeration Engineers designation, "141b") is presently under consideration as a replacement for trichlorofluoromethane as a foam blowing agent. It has a substantially lower ozone depletion index than trichlorofluoromethane. Moreover, 141b displays a 10-15% greater blowing efficiency in rigid foam, and an improved solubility in aromatic polyester polyol, in comparison to trichlorofluoromethane.
1-Chloro-1,1-difluoroethane (hereinafter "142b") is the starting material for the production of polyvinylidene fluoride.
The fluorination of 1,1,1-trichloroethane (hereinafter "140a") to manufacture 142b results in a product stream which includes unreacted starting materials as well as by-products including HCl, vinylidene chloride and 1,1,1-trifluoroethane (hereinafter "143a"). The reactor bottoms include unreacted hydrogen fluoride, pentafluorobutane and possibly small amounts of other organics. Pentafluorobutane is the principal component of reactor tars which accumulate in the reactor bottoms. Vinylidene chloride and pentafluorobutane have boiling points so close to 141b that they cannot be removed by simple distillation. Additional steps for separating 141b from these undesired side products are required, contributing to the overall expense of the process. Moreover, large yield losses are suffered when reactor tars are dumped.
U.S. Pat. No. 3,833,676 discloses a non-catalytic process for the fluorination of 140a with hydrogen fluoride to produce 141b and 142b, without formation of tar substances.